It has heretofore been proposed to restrict the access to cylindrical type locks in the walls of cabinets, etc. to prevent tampering with the lock and to prevent theft of the contents of the cabinet.
There have been a number of solutions for protecting the lock by means of a shroud, a keyhole guard, a keyhole stuffer and the like, as exemplified by the disclosures of the following patents.
In U.S. Pat. No. 1,457,702 to Hoff of June 5, 1923, a pair of spaced apart parallel bars with padlock with terminal locking dogs prevent access to the keyhole by filling the keyhole. This invention has the disadvantage of not fitting in small sized keyholes of cylinder type locks and can only fit if the keyhole is of sufficient size, rectilinear and unobstructed. It, therefore, does not have universal application.
In U.S. Pat. No. 1,206,611 to Strode of Nov. 28, 1916 a guard bar covers the keyhole to prevent access to the keyhole, and in U.S. Pat. No. 3,714,804 to French of Feb. 6, 1973 a shutter covers the keyhole. These inventions have the disadvantage of being difficult to install and each requires permanent bolt or rivet attachment to the cabinet so that they are not portable or detachable.
Other types of lock protectors are exemplified in U.S. Pat. No. 1,590,981 to Lockyer, U.S. Pat. No. 3,623,346 to Curtin or U.S. Pat. No. 3,874,204 to Capri wherein a shroud or cover fits over something which is spaced from the wall such as a lock handle or knob and is anchored by a part fitting under the same in the space. These devices would have no utility with the cylinder locks on tool cabinets or tool boxes because they have no projecting hooked parts and no handles or knobs to fit under for padlocking of a cover or shroud.